US Scientists Engineer 'Mighty Mice'

US researchers have engineered a line of "mighty mice". The breed of mice can run six kilometers (four miles) at a speed of 20 meters (yards) per minute for up to six hours without stopping, according to Richard Hanson, a biochemistry professor at Case Western Reserve University in Cleveland, Ohio.

"They are metabolically similar to Lance Armstrong biking up the Pyrenees; they utilize mainly fatty acids for energy and produce very little lactic acid," said Hanson, the senior author of the article which was published in the Journal of Biological Chemistry.

The genetically engineered mice can eat 60 percent more than wild mice in a control group but remain slim and fit. The "mighty mice" live longer, and some females were able to reproduce much later in life than other mice.

The researchers said some "have had offspring at 2.5 years of age, an amazing feat considering most mice do not reproduce after they are one year old."

Hanson said the strength of the mice was made possible by the fact that they produce very little lactic acid, which forms during intense exercise.